Shock caging features for mems actuator structures

ABSTRACT

Caging structures are disclosed for caging or otherwise reducing the mechanical shock pulse experienced by MEMS device beam structures during events that may cause mechanical shock to the MEMS device. The caging structures at least partially surround the beam such that they limit the motion of the beam in a direction perpendicular to the beam&#39;s longitudinal axis, thereby reducing stress on the beam during a mechanical shock event. The caging structures may be used in combination with mechanical shock-resistant beams.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/412,488, filed on Jan. 23, 2017, entitled “Shock Caging Features forMEMS Actuator Structures, which is a continuation of U.S. patentapplication Ser. No. 15/165,893 filed on 26 May 2016, entitled “ShockCaging Features For MEMS Actuator Structures”, the contents of which areall incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to mechanical shock resistantstructures for microelectromechanical systems (MEMS), and moreparticularly, embodiments relate to shock caging features for MEMSactuator structures.

BRIEF SUMMARY OF THE DISCLOSURE

In accordance with various embodiments of the technology disclosedherein, structures are disclosed for caging or otherwise reducing theshock pulse experienced by MEMS device beam structures during eventsthat may cause mechanical shock to the MEMS device. In one embodiment, aMEMS device includes a beam and a silicon caging structure that at leastpartially surrounds the beam. The beam has a center portion including afirst end and second end, a first hinge directly coupled to the firstend of the center portion, and a second hinge directly coupled to thesecond end of the center portion, where the first hinge and second hingeare thinner than the center portion. The silicon caging structure limitsa maximum displacement of the beam in a direction perpendicular to itslength. In embodiments, the beam is rigid in a direction along itslength and flexible in a direction perpendicular to its length, and thebeam may be between 1 and 7 millimeters long and between 10 and 70micrometers wide.

In one embodiment, the beam is a conductive cantilever, and the centerportion is curved and includes a point of inflection. In anotherembodiment, the beam is a motion control flexure, and the center portionis tapered along its length such that it is widest at its center andnarrowest at its ends.

In one embodiment, the MEMS device includes a moving frame, and thesilicon caging structure is part of the moving frame. In implementationsof this embodiment, at least one of the first hinge and the second hingeis coupled to the moving frame. In further implementations of thisembodiment, the silicon caging structure may include: a protrusionextending parallel to and along the length of the first hinge or thesecond hinge, where the protrusion limits the maximum displacement ofthe beam in a direction perpendicular to its length.

In another embodiment, the MEMS device is an actuator, the beam is amotion control flexure of the actuator, and at least one of the firsthinge and the second hinge is coupled to a frame of the actuator. Inimplementations of this embodiment, the first hinge is coupled to afixed frame of the actuator, and the second hinge is coupled to a movingframe of the actuator.

In a further embodiment, each of the first and second hinges of the beamis coupled to the center portion by a respective forked junction in adirection perpendicular to the length of the cantilever, and therespective forked junction includes a plurality of parallel beams. In animplementation of this embodiment, the silicon caging structureincludes: a protrusion extending parallel to and along the length of thefirst hinge or the second hinge, where the protrusion limits the maximumdisplacement of the cantilever in a direction perpendicular to itslength, and where the cantilever reaches its maximum perpendiculardisplacement when the protrusion contacts one of the forked junctions.

In yet another embodiment of the technology disclosed herein, a MEMSactuator includes: a plurality of silicon beams; and a silicon cagingstructure at least partially surrounding each of the plurality ofsilicon beams, where the silicon caging structure limits a maximumdisplacement of each of the plurality of silicon beams in a directionperpendicular to the silicon beam's length. In implementations of thisembodiment, the MEMS actuator includes a moving frame, the moving frameincludes at least a portion of the silicon caging structure, and one ormore of the plurality of silicon beams is directly coupled to the movingframe.

As used herein, the term “about” in quantitative terms refers to plus orminus 10%. For example, “about 10” would encompass 9-11. Moreover, where“about” is used herein in conjunction with a quantitative term it isunderstood that in addition to the value plus or minus 10%, the exactvalue of the quantitative term is also contemplated and described. Forexample, the term “about 10” expressly contemplates, describes andincludes exactly 10.

Other features and aspects of the disclosure will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, which illustrate, by way of example, the featuresin accordance with various embodiments. The summary is not intended tolimit the scope of the invention, which is defined solely by the claimsattached hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technology, in accordance with one or more variousembodiments, is described in detail with reference to the followingfigures. The drawings are provided for purposes of illustration only andmerely depict typical or example embodiments of the disclosedtechnology. These drawings are provided to facilitate the reader'sunderstanding of the disclosed technology and shall not be consideredlimiting of the breadth, scope, or applicability thereof. It should benoted that for clarity and ease of illustration these drawings are notnecessarily made to scale.

FIG. 1A illustrates a plan view of a comb drive in accordance withexample embodiments of the disclosed technology.

FIG. 1B illustrates a plan view of a bidirectional comb drive actuatorincluding six of the comb drives of FIG. 1A that may use shock-resistantmotion control flexures in accordance with embodiments of the disclosedtechnology.

FIG. 1C is a magnified view of a first comb drive coupled to a secondcomb drive in accordance with embodiments of the disclosed technology.

FIG. 1D illustrates a tapered motion control flexure for an actuatorthat may be used in embodiments to absorb an inertial load duringmechanical shock events.

FIG. 1E illustrates a design for a hinge of a motion control flexurethat may be used in embodiments to reduce stress experienced by thehinges of the motion control flexure during mechanical shock events andnormal operation.

FIG. 2A illustrates a plan view of an MEMS actuator in accordance withexample embodiments of the disclosed technology.

FIG. 2B is a schematic diagram illustrating a cross-sectional view of acantilever of the actuator of FIG. 2A in accordance with exampleembodiments of the disclosed technology.

FIG. 2C illustrates a cantilever having a forked junction design thatmay be implemented in embodiments of the disclosed technology.

FIG. 2D illustrates a cantilever having an S-shaped design that may beimplemented in embodiments of the disclosed technology.

FIG. 2E illustrates a cantilever having an S-shaped design and forkedjunction that may be implemented in embodiments of the disclosedtechnology.

FIG. 2F illustrates an alternative embodiment of a forked junction thatmay be used in the cantilever of FIG. 2E.

FIG. 3A illustrates an example MEMS actuator including an outer frame,inner frame, and shock stops in accordance with the disclosedtechnology.

FIG. 3B is a magnified view of the shock stops of the MEMS actuator ofFIG. 3A.

FIG. 3C illustrates a pair of shock stops that may be implemented inembodiments of the disclosed technology.

FIG. 3D illustrates a pair of shock stops that may be implemented inembodiments of the disclosed technology.

FIG. 4A illustrates a plan view of a section of an example MEMSmulti-dimensional actuator that utilizes shock caging structures inaccordance with example embodiments of the present disclosure.

FIG. 4B illustrates a shock caging structure for caging a cantilever inaccordance with an embodiment of the present disclosure.

FIG. 4C illustrates a shock caging structure for caging a cantilever inaccordance with an embodiment of the present disclosure.

FIG. 4D illustrates a shock caging structure for caging a motion controlflexure in accordance with an embodiment of the present disclosure.

FIG. 4E illustrates a shock caging structure for caging a motion controlflexure in accordance with an embodiment of the present disclosure.

FIG. 5A illustrates an example model of a mechanical shock event of aMEMS actuator including shock caging structures for its cantilevers andmotion control flexures.

FIG. 5B illustrates an example model of a mechanical shock event of aMEMS actuator not including shock caging structures for its cantileversand motion control flexures.

FIG. 6A illustrates an actuator with a moving frame, and an image sensormounted on the actuator, in accordance with an embodiment of the presentdisclosure.

FIG. 6B illustrates a package housing for covering the image sensor ofFIG. 6A, the packaging housing including shock stops for reducing thegap between the package housing and the moving frame, in accordance withan embodiment of the present disclosure.

FIG. 6C illustrates a cross-section of an assembled actuatoroptoelectronic package, in accordance with an embodiment of the presentdisclosure.

FIG. 6D illustrates a cross-section of an assembled actuatoroptoelectronic package, in accordance with an embodiment of the presentdisclosure.

FIG. 6E illustrates a cross-section of an assembled actuatoroptoelectronic package, in accordance with an embodiment of the presentdisclosure.

FIG. 7 is an exploded perspective view of an example image sensorpackage utilized in accordance with various embodiments of the disclosedtechnology.

The figures are not intended to be exhaustive or to limit the inventionto the precise form disclosed. It should be understood that theinvention can be practiced with modification and alteration, and thatthe disclosed technology be limited only by the claims and theequivalents thereof.

DETAILED DESCRIPTION

In accordance with various embodiments of the disclosed technology,structures are disclosed for caging or otherwise reducing the mechanicalshock pulse experienced by MEMS device beam structures during eventsthat may cause mechanical shock to the MEMS device. The cagingstructures described herein may at least partially surround cantilevers,flexures, or other beam structures. This limits the motion of the beamin a direction perpendicular to the beam's longitudinal axis, therebyreducing stress on the beam and preventing possible breakage or damagein the event of a mechanical shock.

For example, in the event that a device (e.g., a cellphone) with aninstalled MEMS device is dropped from a height that may produce asignificant shock force (e.g., greater than one meter), the cagingstructures disclosed herein may prevent damage to the beam structures ofthe MEMS actuator when the device hits the ground. By preventing thebeams from experiencing large amplitude oscillations perpendicular totheir length or otherwise moving excessively during the impact of thedrop, the caging structures help reduce stress on the beam.

In embodiments, the disclosed shock caging structures may be used incombination with shock-resistant MEMS device structures (e.g., shockresistant beam structures). In implementations, the shock-resistantstructures may reduce load on the MEMS actuator and resist deformationduring events that may cause shock to the MEMS actuator. Accordingly, byimplementing a combination of shock caging features with shock-resistantstructures, the reliability of a MEMS device may be improved.

FIGS. 1-7 illustrate MEMS actuators for moving an optoelectronic devicethat may implement shock resistant structures in accordance withparticular embodiments of the technology disclosed herein. It should benoted that although the resistant caging MEMS structures will bedescribed primarily with reference to the example MEMS actuators ofFIGS. 1-7, one having skill in the art would appreciate that the shockresistant structures described herein could be implemented in other MEMSapparatuses including moving beams that may be subject to mechanicalshock events.

FIGS. 1A-1B illustrate plan views of a comb drive 10 and bidirectionalcomb drive actuator 20 including six comb drives 10 a-f in accordancewith example embodiments of the present disclosure. As illustrated inFIG. 1A, each comb drive 10 includes comb finger arrays 15 and 16. Eachcomb finger array 15 and 16 includes a respective spine (14, 12) andplurality of comb fingers (13, 11).

Bidirectional Comb drive actuator 20 includes first and second framepieces 22 a-22 b, and first and second motion control flexures 24 a-24b. Although not shown in detail in FIG. 1B, it will be understood that,as shown in FIG. 1A, for each comb drive 10 a-f, comb fingers 11 and 13extend substantially from left to right, and vice versa, in comb fingerarrays 15 a-f and 16 a-f. Moreover, it will be understood that spines 12and 14 run substantially vertically from first frame piece 22 a tosecond frame piece 22 b, i.e., substantially in parallel with motioncontrol flexures 24 a-24 b. This is illustrated by FIG. 1C, which showsa first comb drive 10 b coupled to a second comb drive 10 c.

As illustrated in this embodiment, spine 14 is attached to second framepiece 22 b, while spine 12 is attached to first frame piece 22 a. Duringoperation, as comb finger arrays 15 and 16 of each comb drive 10 a-10 fare attracted to or repelled from one another by electrostatic forces,movement occurs such that first frame piece 22 a likewise moves in adirection when the second frame is fixed (e.g., in the positive Xdirection in FIG. 1B). One of skill in the art will appreciate, uponstudying the present disclosure, that electrostatic forces and othermotive forces may be developed between each pair of comb finger arrays15 and 16 by methods other than applying voltage, without departing fromthe spirit of the present disclosure. For example, charge may be appliedto comb finger arrays 15 and 16.

In various embodiments, spines 12 and 14 and first and second framepieces 22 a and 22 b may be dimensioned wide and deep enough to be rigidand not flex substantially under an applied range of electrostatic orother motive forces. For example, in particular embodiments spines 12and 14 may be about 20 to 100 micrometers wide and about 50 to 250micrometers deep, and first and second frame pieces 22 a and 22 b may belarger than about 50 micrometers wide and about 50 to 250 micrometersdeep.

In one embodiment, during operation of comb drive actuator 20, when combfinger arrays 15 a and 16 a are electrified (e.g., in the mannerdescribed above), a motive force is applied with respect to first andsecond frame pieces 22 a-22 b such that either first or second framepiece 22 a-22 b moves substantially horizontally from an initialposition with respect to second or first frame piece 22 a-22 b,depending upon which of first and second frame piece 22 a-22 b ismechanically fixed. Once comb finger arrays 15 a and 16 a are no longerelectrified, first or second frame pieces 22 a-22 b move back to theinitial state due to the spring restoring force of first and secondmotion flexures 24 a and 24 b. Further to this implementation, movementin a substantially opposite direction is achieved (e.g., in the oppositeX direction in FIG. 1B), in addition to the movement resulting from combdrive 10 a, when comb finger arrays 15 c and 16 c of comb drive 10 c areelectrified. Likewise, bidirectional movement in these two directions(i.e., positive and negative X direction in the drawing) may be achievedby electrifying the comb finger arrays of comb drives 10 b, 10 d, and 10e-f.

In various embodiments, spines 12 and 14 of comb finger arrays 15 a-fand 16 a-f may be attached to first and/or second frame pieces 22 a-b indifferent configurations to achieve different purposes. For example, inone embodiment, for each comb drive 10 a-10 f, spine 12 is attached tofirst frame piece 22 a while spine 14 is attached to second frame piece22 b. Such a configuration results in a parallel cascade of comb drives10 a-f that may increase the electrostatic force ultimately applied tofirst and second frame pieces 22 a-b. In another example embodiment,comb drives 10 a-10 f are arranged in a back-to-back fashion to achievebidirectional movement, as described above. While this back-to-backarrangement was described above with regard comb drives 10 a-f—i.e., sixcomb drives 10—a different number of comb drives may be used to achievebidirectional movement.

In one embodiment, a comb finger array, for example, 16 a, 16 c, 16 e or15 b, 15 d, 15 f of each comb drive 10 a-10 f may be tied to a commonpotential (e.g., ground or some other positive or negative voltage) thatacts as a reference for the other three comb finger arrays. Given thisreference, the comb finger arrays that are not tied to a commonpotential may be electrified depending upon the direction of movementrequired.

For example, consider an embodiment where comb finger arrays 15 a, 16 b,15 c, 16 d, 15 e and 15 f of comb drives 10 a-10 f are tied to a commonground. In this embodiment, movement of comb drive actuator 20 may beeffectuated by applying a positive or negative voltage (e.g., relativeto ground or other common reference) to comb finger array 16 a, hencecausing comb finger array 16 a to be attracted to comb finger array 15a. Assuming second frame piece 22 b is fixed, this attraction would, inthis example, cause first frame piece 22 a to move to the left in FIG.1B. Further to this illustration, electrifying comb finger array 15 bmay entail applying thereto a positive or negative voltage 15 b, hencecausing comb finger array 15 b to be attracted to comb finger array 16b. This attraction would, in this instance, cause first frame piece 22 ato move to the right in FIG. 1B, assuming again that second frame piece22 b is fixed.

In further embodiments, the motive force developed by a comb drive 10 amay differ from the motive force developed by another comb drive 10 b-10f. For example, voltages of different magnitudes may be applied to someor all of comb finger arrays 15 b, 15 d, and 15 f, or whichever combfinger arrays are not tied to a common potential. In some embodiments,for comb finger arrays 15 b, 15 d, and 15 f to maintain differentvoltage levels, or electrostatic or charge states, the comb fingerarrays may be electrically separate (or isolated) from one another.

The movement of first or second frame pieces 22 a-22 b and comb fingerarrays 15 a-f or 16 a-f of each comb drive 10 a-10 f may be directedand/or controlled to some extent by first and second motion controlflexures 24 a-24 b. In this particular embodiment, for example, firstand second motion control flexures 24 a-24 b are substantially flexibleor soft in the horizontal direction (i.e., in the direction of combfingers 11 and 13) and substantially stiff or rigid in the verticaldirection (i.e., in the direction of spines 12 and 14). Accordingly,first and second motion control flexures 24 a-24 b allow comb drive 10to effect bidirectional movement horizontally (i.e., in the X directionFIG. 1B) while substantially restricting the movement in the verticaldirection (i.e., in the Y direction in FIG. 1B).

The arrangement of first and second motion control flexures 24 a-24 bmay be referred to, in some embodiments, as a double parallel flexuremotion control. Such a double parallel flexure motion control mayproduce nearly linear motion, but there may be a slight run-out known asarcuate motion. Nevertheless, the gap on one side of comb fingers 11 maynot be equal to the gap on the other side of comb fingers 11, and thismay be used advantageously in design to correct for effects such asarcuate motion of a double parallel flexure motion control. Inembodiments, additional structures may be used to control the motion offirst and second frame pieces 22 a-22 b with respect to one another.

In the illustrated embodiment, first and second flexures 24 a-24 binclude thinner portions 24 a-2 and 24 b-2 on the respective endsthereof. These thinner portions may allow bending when, for example,there is a translation of first frame piece 22 a with respect to secondframe piece 22 b or vice versa (i.e., in the X direction in FIG. 1B). Inembodiments, the thicker portion 24 a-1 and 24 b-1 of first and secondflexures 24 a and 24 b may be dimensioned to be about 10 to 50micrometers (μm) wide (i.e., width in x direction of FIG. 1B), and thethinner portions 24 a-2 and 24 b-2 may be dimensioned to be about 1 to10 μm wide. In various embodiments, any number and type of motioncontrols may be used as desired to control or limit the motion of combfinger arrays 15 or 16. Controlled motion may enhance the overallprecision with which comb drive actuator 20 effects movement, orpositions a device such as, for example, an image sensor in a smartphonecamera. In addition, controlled motion aids in avoiding a situation inwhich comb fingers 11 and 13 snap together. For example, controlledmotion may generally be effected by creating a lower level of stiffnessin desired direction of motion of comb fingers 15 and 16, while creatinga higher level of stiffness in all undesired degrees of freedom,especially in the direction orthogonal to the motion of comb fingers 15and 16 in the plane of comb drive actuator 20. By way of example, thismay be done using a double parallel flexure type motion control.

In various embodiments, motion control flexures 24 a and 24 b may bedesigned to improve the shock performance of a MEMS actuator device. Insuch embodiments, motion control flexures 24 a and 24 b may be designedto absorb a force or load during a shock event (e.g., dropping a devicecontaining the MEMS actuator). For example, in particular embodiments,motion control flexures 24 a and 24 b may be designed to survive theinertial load due to a motion stage for the MEMS actuator (notillustrated) and at least one of the three comb array pairs (10 a, 10 c,10 e), and (10 b, 10 d, 10 f). In specific implementations of theseembodiments, this inertial load may be between 200 and 800 mN.

FIG. 1D illustrates a particular design for a tapered motion controlflexure 24 that may be used in embodiments to absorb an inertial loadduring shock events. In embodiments, motion control flexure 24 maysurvive a loading force between 100 and 400 mN before entering a buckledstate (i.e., before deforming).

As shown, motion control flexure 24 includes two thin, soft hinges 24-2and a wide, stiff rod 24-1 connecting the two hinges. In embodiments,rod 24-1 may be between 1 and 4 millimeters (mm) long in the x directionand between 10 and 50 μm wide in the y direction. In embodiments, hinges24-2 may be between 0.05 and 0.3 mm long in the x direction and between1 and 10 μm wide in the y direction. In these embodiments, thedimensions of hinges 24-2 may be optimized to achieve a requiredstiffness or to avoid buckling. As shown in this particular embodiment,rod 24-1 is tapered along its length such that it is widest at itscenter and narrowest at it ends. This tapered design, in someembodiments, permits motion control flexure 24 to survive a largerloading force before entering a buckled state. In particularimplementations of this embodiment, tapered rod 24-1 may be between 35and 50 μm wide at its center and between 20 and 40 μm wide at its ends.In one particular embodiment, stiff-rod 24-1 is about 50 μm wide at itscenter, about 35 μm wide at its end, and capable of taking an inertialload of about 280 mN before buckling. In alternative embodiments,stiff-rod 24-1 may be uniformly wide along its entire length.

FIG. 1E illustrates a particular design for hinge 24-2′ for a motioncontrol flexure (e.g., flexure 24) that may be used in embodiments toreduce stress experienced by the hinges of the motion control flexureduring shock events and normal operation. As illustrated, hinge 24-2′ istapered along its length such that it is narrowest at its center andwidest at its ends (in the y direction). For example, hinge 24-2′ may beabout 5 μm wide at its center and about 6 μm wide at its ends (in the ydirection). Although not shown in FIG. 1E, hinge 24-2′ is also taperedin the z direction such that it is thickest at its ends and thinnest atits center. In other words, hinge 24-2′ has a three-dimensionalhourglass geometry. The hourglass geometry increases the amount ofmaterial on the end portions of hinge 24-2′ (e.g., the ends connected tothe actuator and rod of the flexure) while reducing the amount ofmaterial on the center portion of hinge 24-2′. As the end portions ofhinge 24-2′ tend to be the weakest portions of the motion controlflexure, the hourglass geometry may redistribute the stress experiencedduring a shock event, resulting in a more durable flexure.

FIG. 2A illustrates a plan view of an example MEMS multi-dimensionalactuator 40 in accordance with example embodiments of the presentdisclosure. As illustrated in this embodiment, actuator 40 includes anouter frame 48 (divided into four sections) connected to inner frame 46by one or more spring elements or flexures 80, four bidirectional combdrive actuators 20 a-d, and one or more cantilevers 44 a-d including afirst end connected to one end of comb drive actuators 20 a-d and asecond end connected to inner frame 46. Although FIG. 2A illustrates anexample actuator 40 including four comb drive actuators 20, in otherembodiments, actuator 40 may include a different number of comb driveactuators 20.

In embodiments, actuator 40 includes an anchor 42 that is rigidlyconnected or attached to first and/or second frame pieces 22 a-22 b ofone or more comb drive actuators 20, such that anchor 42 is mechanicallyfixed with respect thereto. Thus, for example, if first frame piece 22 ais attached to anchor 32, movement of second frame piece 22 b relativeto first frame piece 22 a may also be considered movement relative toanchor 42.

During operation of actuator 40, comb drive actuators 20 a-d may apply acontrolled force between inner frame 46 and anchor 42. One or more combdrive actuators 20 a-d may be rigidly connected or attached to anchor42, and anchor 42 may be mechanically fixed (e.g., rigidly connected orattached) with respect to outer frame 48. In one embodiment, a platformis rigidly connected or attached to outer frame 48 and to anchor 42. Inthis manner, the platform may mechanically fix outer frame 48 withrespect to anchor 42 (and/or vice versa). Inner frame 46 may then movewith respect to both outer frame 48 and anchor 42, and also with respectto the platform. In one embodiment, the platform is a silicon platform.The platform, in various embodiments, is an optoelectronic device, or animage sensor, such as a charge-coupled-device (CCD) or acomplementary-metal-oxide-semiconductor (CMOS) image sensor.

In embodiments, the size of actuator 40 may be substantially the same asthe size as the platform, and the platform may attach to outer frame 48and anchor 42, thus mechanically fixing anchor 42 with respect to outerframe 48. In another embodiment of actuator 40, the platform is smallerthan actuator 40, and the platform attaches to inner frame 46. In thisparticular embodiment, outer frame 48 is fixed (or rigidly connected orattached) relative to anchor 42, and inner frame 46 is moved by thevarious comb drive actuators 20 a-d.

In one embodiment, two comb drive actuators 20 a and 20 d actuate alonga first direction or axis in the plane of actuator 40 (e.g., east/west,or left/right), and two comb drive actuators 20 b and 20 c actuate alonga second direction or axis in the plane of actuator 40 (e.g.,north/south, or top/bottom). The first and second directions may besubstantially perpendicular to one another in the plane of actuator 40.

Various other configurations of comb drive actuators 20 a-d arepossible. Such configurations may include more or less comb drives 10 ineach of the comb drive actuators 20 a-d, and various positioning and/orarrangement of comb drive actuators 20 a-d, for example, to enableactuation in more or less degrees of freedom (e.g., in a triangular,pentagonal, hexagonal formation, or the like).

In embodiments, cantilevers 44 a-d are relatively stiff in therespective direction of motion of the respective comb drive actuators 20a-d, and are relatively soft in the in-plane orthogonal direction. Thismay allow for comb drive actuators 20 a-d to effect a controlled motionof inner frame 46 with respect to anchor 42 and hence with respect toouter frame 48. In embodiments, illustrated by FIG. 2A, outer frame 48is not continuous around the perimeter of actuator 40, but is brokeninto pieces (e.g., two, three, four, or more pieces). Alternatively, inother embodiments, outer frame 48 may be continuous around the perimeterof actuator 40. Similarly, inner frame 46 may be continuous or may bedivided into sections.

In various embodiments, electrical signals may be delivered to combdrive actuators 20 a-d via routing on or in cantilevers 44 a-d. In someinstances, two or more different voltages may be used in conjunctionwith comb drive actuator 20 a. In such instances, two electrical signalsmay be routed to comb drive actuator 20 a via first and secondconductive layers 45 and 47, respectively, of cantilever 44 a. Oncedelivered to comb drive actuator 20 a, the two electrical signals may berouted, for example, via first frame piece 22 a, to comb finger arrays16 a and 15 b, respectively.

In another example implementation of actuator 40, two electrical signalsused to develop motive forces in comb drive actuator 20 b may also beused to develop similar motive forces in comb drive actuator 20 c. Insuch an implementation, rather than routing these two electrical signalsto comb drive actuator 20 c through cantilever 44 c, the two electricalsignals may be routed to comb drive actuator 20 c from comb driveactuator 20 b. By way of example, this may entail routing the twoelectrical signals from an electrical contact pad 84, through cantilever44 b to a first frame piece 22 a of comb drive actuator 20 b. Inaddition, the two electrical signals may be routed from first framepiece 22 a via flexures 24 a-b (respectively) and second frame piece 22b to anchor 42. The two electrical signals may then be routed throughanchor 42 to comb drive actuator 20 c. It will be appreciated thatvarious routing options may be exploited to deliver electrical signalsto comb drive actuators 20 a-d. For example, multiple routing layers maybe utilized in anchor 42, in first or second frame pieces 22 a/b, and/orin first and second flexures 24 a/b.

FIG. 2B is a schematic diagram illustrating a cross-sectional view of aportion of a cantilever 44 in accordance with example embodiments of thepresent disclosure. As illustrated in FIG. 2B, cantilever 44 includesfirst and second conductive layers 45 and 47, and first and secondinsulating layers 43 and 49. First and second conductive layers 45 and47 may, in some example implementations, serve as routing layers forelectrical signals, and may include polysilicon and/or metal. Insulatinglayers 43 and 49 may provide structure for first and second conductivelayers 45 and 47. In alternative embodiments of cantilever 44, the orderof the conductive and insulating layers may be switched such that layers43 and 49 are conductive layers and layers 45 and 47 are insulatinglayers.

In one example implementation of cantilever 44, insulating layers 43 and49 include silicon dioxide, second conductive layer 47 includes metal,and first conductive layer 45 includes polysilicon. In a variant of thisexample, a coating (e.g., oxide or the like) may cover second conductivelayer 47, e.g., to provide insulation against shorting out when cominginto contact with another conductor. Second insulating layer 49 may be athin layer that includes oxide or the like. Additionally, firstconductive layer 45, in some instances, may be relatively thick(compared to the other layers of cantilever 44), and may, for example,include silicon, polysilicon, metal, or the like. In such instances,first conductive layer 45 may contribute more than the other layers tothe overall characteristics of cantilever 44, including, for example,the nature, degree, or directionality of the flexibility thereof.

Additional embodiments of cantilever 44 (and cantilevers 44 a-d) mayinclude additional conductive layers, such that additional electricalsignals may be routed via the cantilever 44. In some embodiments,cantilevers 44 a-d may be manufactured in a similar fashion to flexures24 a-24 b, though the sizing may be different between the two. Moreover,as would be appreciated by one having skill in the art, additionalmaterials may be used to form the various layers of cantilever 44.

In various embodiments, outer cantilevers 44 may be designed to beresistant to mechanical shock events (e.g., in the event a deviceincluding MEMS actuator 40 is dropped). In such embodiments, eachcantilever 44 may be designed such that it i) experiences lessdisplacement stress during shock; ii) experiences less radial stiffnessduring shock; and iii) withstands a high load without buckling. In someembodiments, outer cantilevers 44 may be designed such that theyexperience a peak stress of less than about 1900 MPa along their length,and less than about 2100 MPa along their width, in the event of a shockFIGS. 2C-2F illustrate four example designs of shock-resistant outercantilevers that may be implemented in embodiments of the disclosure.

FIG. 2C illustrates an outer cantilever 44 e having a forked junctiondesign. As shown, cantilever 44 e includes a forked junction 44 e-1 atits center. The forked-junction 44 e-1 at the center includes anaperture 44 e-2 and is wider (in Y direction) than the sides 44 e-3 ofouter cantilever 44 e. In various embodiments, the width (in Ydirection) of aperture 44 e-2 is between 0.02 and 0.04 millimeters, themaximum width of the forked junction 44 e-1 is between 0.06 and 0.12millimeters, and the width of sides 44 e-3 is between 0.012 and 0.050millimeters. In further embodiments, the total length (in X direction)of cantilever 44 e is between 4.5 and 7 millimeters. In alternativeembodiments, cantilever 44 e may include additional forks (and henceapertures) at its center (e.g. 3, 4, etc.).

FIG. 2D illustrates an outer cantilever 44 f having an S-shaped design.It should be noted that although cantilever 44 f primarily appearsstraight along its length in FIG. 2D, it is curved and has a point ofinflection (hence the “S-shape”) along its length that improvesresilience in the event of a mechanical shock by adding flexibility tocantilever 44 f. In this embodiment, the two roots or connecting ends 44f-1 of cantilever 44 f couple to a center portion 44 f-3 via a thinnerportion or hinge 44 f-2. Cantilever 44 f is widest (in Y direction) atits roots 44 f-1 and narrowest at the junction 44 f-2 between roots 44f-1 and center portion 44 f-3. In various embodiments, the total length(x1) of cantilever 44 f is between 4.5 and 7 millimeters, and the width(y1) of center portion 44 f-3 is between 0.012 and 0.030 millimeters.

FIG. 2E illustrates an outer cantilever 44 g having the S-shaped designof cantilever 44 f and the added feature of a “toothbrush” shaped orforked junction 44 g-1 at each end for relieving stress on cantilever 44g. As illustrated, outer cantilever 44 g includes a center portion 44g-3 with ends coupled to end portions 44 g-4 that attach to roots 44g-2. In various embodiments, the total length (x1) of cantilever 44 g isbetween 4.5 and 7 millimeters, and the width (y2) of center portion 44g-3 is between 0.012 and 0.030 millimeters.

The forked junction 44 g-1 couples each end of center portion 44 g-3 toa respective end portion 44 g-4 in a direction perpendicular (i.e., Ydirection) to the length of cantilever 44 g. Each junction 44 g-1includes a plurality of beams 44 g-5 that give the junction 44 g-1 theappearance of a toothbrush. Although each junction 44 g-1 is illustratedas having thirteen beams 44 g-5 in this embodiment, in alternativeembodiments the number of beams 44 g-5 may be decreased or increased(e.g., from 2 to 15) to improve the performance of cantilever 44 gduring a mechanical shock event (e.g., by reducing peak stress). Asillustrated in this particular embodiment, in one junction the endportion 44 g-4 is below (Y direction) its corresponding center portion44 g-3, and in the other junction the end portion 44 g-4 is above (Ydirection) its corresponding center portion 44 g-3. Also illustrated inthis particular embodiment, the root 44 g-2 attached to the end portion44 g-4 by hinge 44 g-6 below the center portion 44 g-3 points upward,whereas the other root 44 g-2 points downward. In particularembodiments, the total width (y1) of a forked junction 44 g-1, includingthe end of center portion 44 g-3, end portion 44 g-4, and beams 44 g-5,is between 0.040 and 0.150 millimeters.

FIG. 2F illustrates an alternative embodiment of a forked junction 44g-1′ that may be used in place of forked junction 44 g-1 in cantilever44 g to relieve stress. As illustrated in this particularimplementation, the end 44 g-3′ of the center portion of cantilever 44 gis tapered along its length (X direction) such that its width (Ydirection) decreases in a direction toward the root (not shown) of thecantilever. The end 44 g-3′ attaches to a corresponding tapered endportion 44 g-4′ that is tapered along its length such that its widthdecreases in a direction away from the root. Because the width (Ydirection) of the two ends 44 g-4′ and 44 g-3′ is substantially lessalong their junction point, this tapered design permits a greater lengthof beams 44 g-5′ in a direction roughly perpendicular to cantilever 44 g(Y direction).

A hinge 44 g-6′ extends from a root (not shown) and connects to forkedjunction end 44 g-4′. In embodiments, hinge 44 g-6′ may have the samethree-dimensional hourglass geometry as described above with respect tohinge 24-2′ of FIG. 1E. As the junctions connecting hinge 44 g-6′ to thecantilever root and end 44 g-4′ may be the weakest portions of the outercantilever, the hourglass geometry may redistribute the stressexperienced during a shock event, resulting in a more durablecantilever. In embodiments, hinge 44 g-6′ may be about 5 μm wide at itscenter and about 6 μm wide at its ends (in the y direction), and about0.2 mm long (in the x direction).

Referring back to FIG. 2A, actuator 40 includes one or more flexures orspring elements 80 connecting inner frame 46 to outer frame 48. Flexures80 may be electrically conductive and may be soft in all movementdegrees of freedom. In various embodiments, flexures 80 route electricalsignals between electrical contact pads 82 on outer frame 48 toelectrical contact pads 84 on inner frame 46. These electrical signalsmay subsequently be routed to one or more comb drive actuators 20through one or more cantilevers 44 a-44 d. In example implementations,flexures 80 come out from inner frame 46 in one direction, twodirections, three directions, or in all four directions.

In one embodiment, actuator 40 is made using MEMS processes such as, forexample, photolithography and etching of silicon. Actuator 40, in somecases, moves +/−150 micrometers in plane, and flexures 80 may bedesigned to tolerate this range of motion without touching one another(e.g., so that separate electrical signals can be routed on the variousspring elements 80). For example, flexures 80 may be S-shaped flexuresranging from about 1 to 5 micrometers in thickness, about 1 to 40micrometers wide, and about 150 to 1000 micrometers by about 150 to 1000micrometers in the plane.

In order for flexures 80 to conduct electricity well with lowresistance, flexures 80 may contain, for example, heavily dopedpolysilicon, silicon, metal (e.g., aluminum), a combination thereof, orother conductive materials, alloys, and the like. For example, flexures80 may be made out of polysilicon and coated with a roughly 0.2˜1micrometer thick metal stack of Aluminum, Nickel, and Gold. In oneembodiment, some flexures 80 are designed differently from otherflexures 80 in order to control the motion between outer frame 48 andinner frame 46. For example, four to eight (or some other number) offlexures 80 may have a thickness between about 10 and 250 micrometers.Such a thickness may somewhat restrict out-of-plane movement of outerframe 48 with respect to inner frame 46.

In particular embodiments, flexures 80 are low stiffness flexures thatoperate in a buckled state without failure, thereby allowing thestiffness of the flexures to be several orders of magnitude softer thanwhen operated in a normal state. In these embodiments, a buckled section(i.e., flexible portion) of flexures 80 may be designed such that across section of the flexible portion along its direction of bending(i.e., thickness and width) is small, while its length is relativelylong. Particular embodiments of flexures 80 are described in greaterdetail in U.S. patent application Ser. No. 14/677,730 titled “LowStiffness Flexure”, filed Apr. 2, 2015.

As noted above with respect to FIG. 2A, a MEMS actuator may be designedwith an outer frame 48 coupled to an inner frame 46 by a plurality offlexures 80. During operation, inner frame 46 may collide with outerframe 48 in the event of a sudden shock. Accordingly, in embodiments,shock stops may be included in the outer and inner frames to protect theMEMS actuator structure in the event of shock.

FIGS. 3A-3B illustrate one such embodiment of a MEMS actuator 100including shock stops. As illustrated in this particular embodiment,MEMS actuator 100 comprises an inner frame 110 and an outer frame 120that may be coupled by a plurality of flexures (not pictured). As shownin this embodiment, outer frame 120 includes four electrical bars121-124. In other embodiments outer frame 120 may be one piece. A pairof shock stops 127 and 111 corresponding to outer frame 120 and innerframe 110, respectively. In this particular embodiment of actuator 100,four pairs of shock stops 127 and 111 (one for each corner) are presentto absorb kinetic energy of shock collisions between outer frame 120 andinner frame 110 in the event of a shock. However, as would beappreciated by one having skill in the art, any number of shock stoppairs could be implemented in alternative implementations of a MEMSactuator or other MEMS device that experiences collisions between twoportions of the device.

In various embodiments, shock stops 127 and 111 may be designed tomaximize the amount of kinetic energy they can absorb upon impact (e.g.,when horizontal or vertical stop 127 collides with stop 111) due to ashocking event without experiencing permanent deformation. For example,in embodiments shock stops 127 and 111 may be designed to absorb acombined kinetic energy of between 100 and 400 μJ. In particularembodiments, shock stops 127 and 111 may absorb a combined kineticenergy of between 300 and 400 μJ.

FIGS. 3C-3D illustrates two exemplary designs of shock stops 127 and 111that may be implemented in embodiments of the technology disclosedherein. FIG. 3C illustrates shock stops 127 a and 111 a comprising aplurality of circular, staggered apertures 160. In the event of a shock,surface 127 a-2 of stop 127 a contacts surface 111 a-2 of shock 111 a.As illustrated in this particular embodiment, the apertures 160 arespaced apart in a concentrated, hexagonal pattern. In variousembodiments, the diameters of the circular apertures may be between0.010 and 0.022 millimeters. In particular embodiments, the diameter ofthe circular apertures is about 16 μm. In particular embodiments, shockstops 127 a and 111 a may absorb a combined energy of about 350 μJ andeach deform up to about 40 μm before breaking. In alternativeimplementations of shock stops 127 a and 11 a, apertures 160 may befilled with epoxy glue or other energy absorbing material to adjusttheir stiffness as well as capability of absorbing energy, and/orarranged in a different pattern (e.g., triangular, rectangular, linear,or other pattern). In various embodiments, the total length (x₁) ofshock stop 127 a is between 0.250 and 1.000 millimeters, and the totalwidth (y₁) of shock stop 127 a is between 0.0250 and 1.000 millimeters.In various embodiments, the total length (x₂) of shock stop 111 a isbetween 0.300 and 1.200 millimeters, and the total width (y₂) of shockstop 111 a is between 0.0250 and 1.000 millimeters.

FIG. 3D illustrates shock stops 127 b and 111 b comprising a pluralityof square, staggered apertures 170. Similar to FIG. 3C, the apertures170 are spaced apart in a concentrated, hexagonal pattern. In particularembodiments, shock stops 127 b and 111 b may absorb a combined energy ofabout 300 μJ and each deform up to about 15 μm before breaking. Inalternative implementations of shock stops 127 b and 111 b, apertures170 may be filled with epoxy glue or other energy absorbing material toadjust their stiffness as well as capability of absorbing energy, and/orarranged in a different pattern (e.g., triangular, rectangular, linear,or other pattern).

In yet further embodiments of the technology disclosed herein, otheralternative shock stop designs may be implemented to tune the maximumenergy they can absorb and the maximum amount of distance they maydisplace without breaking. For example, horizontal or vertical slits maybe used instead of or in combination with the aforementioned apertures.

FIG. 4A illustrates a plan view of a section of an example MEMSmulti-dimensional actuator 200 that utilizes shock caging structures inaccordance with example embodiments of the present disclosure. Asillustrated in this embodiment, actuator 200 includes four bidirectionalcomb drive actuators 20 a-d, and one or more cantilevers 20 a-dincluding a first end connected to one end of bidirectional comb driveactuators 20 a-d and a second end connected to an inner frame 250. Likeactuator 40, actuator 200 may move in multiple degrees of freedom undera control force applied by comb drive actuators 20 a-d between innerframe 250 and a central anchor (not shown).

In this embodiment, actuator 200 additionally includes shock cagingstructures 400, 500, 600, and 700 that limit the motion or maximumdisplacement of cantilevers 44 a-d and motion control flexures 24 ofcomb drive actuators 20 a-d in a direction perpendicular to theirlength. This limits or prevents large amplitude oscillations fromoccurring perpendicular to the length of the beam. In variousembodiments, the shock caging structures may be solid silicon structuresthat do not displace substantially when they are contacted bycantilevers 44 a-d or motion control flexures 24. In implementations ofthese embodiments, the shock caging structures are shaped such that thecantilevers 44 a-d or motion control flexures 24 contact a maximumamount of the surface area of the caging structure during a shock event.

As illustrated in this embodiment, actuator 200 includes four distinctshock caging configurations or structures: structures 400 and 500 forcaging cantilevers 44 a-44 d, and structures 600 and 700 for cagingmotion control flexures 24. As would be appreciated by one having skillin the art, in various embodiments the shock caging structures need notbe limited to the precise configurations illustrated herein, and may beimplemented to limit the movement of any moving beam in a MEMS device.

Shock caging structures 400 and 500 limit the motion of cantilevers 44a-44 d and may be formed as a part of inner frame 250 or a moving frame22 a of comb drive actuators 20 a-20 d. For example, as illustrated inthis embodiment, shock caging structure 400 is formed as part of amoving of frame 22 a of a comb drive actuator 20 a-20 d whereas shockcaging structure 500 is formed as part of the inner frame 250.

Shock caging structures 600 and 700 limit the motion of motion controlflexures 24 and may be formed as a part of the fixed or moving frames(e.g., frame pieces 22 a-22 b) of comb drive actuators 20 a-20 d. Forexample, shock caging structures 700 may be a part of the fixed frame 22b of comb drive actuators 20 a-20 d whereas shock caging structures 600may be a part of the moving frame 22 a of comb drive actuators 20 a-20d. The caging structures may be formed by shifting comb drive actuators20 a-20 d further away from the center of the actuator.

FIG. 4B illustrates a shock caging structure 400 for caging a cantilever44 in accordance with an embodiment. Caging structure 400 (e.g., a rigidsilicon structure) surrounds an end of cantilever 44. In thisembodiment, caging structure 400 is a part of a moving frame 22 a of acomb drive actuator 20.

Caging structure 400 includes a protrusion 420 above hinge 44 g-6′ thatextends parallel to and past the hinge. In this example, protrusion 420terminates above end 44 g-4′ of the forked junction 44 g-1′.Accordingly, in the event of a shock, end 44 g-4′ contacts stiffprotrusion 420 and does not vertically displace in the y direction paststiff protrusion 420. Following this configuration, the motion of thinhinge 44 g-6′, which may be the weakest portion of cantilever 44, issubstantially limited during a shock event. For example, with the cagingstructure 400, hinge 44 g-6′ may displace about 10 times less in the ydirection. In alternative embodiments, protrusion 420 may terminateabove end 44 g-3′ of the forked junction 44 g-1′ or even further.

The length of protrusion 420 and the vertical gap between forkedjunction 44 g-1′ and caging structure 420 may be tuned in variousembodiments to maximize the amount of mechanical shock protectionprovided while ensuring that cantilever 44 has enough space to moveduring regular operation. In specific embodiments, protrusion 420 may bebetween 150 and 300 micrometers long, and the gap between end 44 g-4′and caging structure 320 b (below or above the forked junction) may bebetween 3 and 20 micrometers.

FIG. 4C illustrates a shock caging structure 500 for a caging acantilever 44 in accordance with an embodiment. A caging structure 500(e.g., a rigid silicon structure) surrounds an end of a cantilever 44.In this embodiment, caging structure 500 is a part of inner frame 250 ofactuator 200.

Caging structure 500 includes a protrusion 520 below hinge 44 g-6′ thatextends parallel to and past the hinge. In this example, protrusion 520terminates below end 44 g-4′ of the forked junction 44 g-1′.Accordingly, in the event of a mechanical shock, end 44 g-4′ contactsstiff protrusion 520 and does not displace downward in the y directionpast stiff protrusion 520, or upward in the y direction past the wall ofinner frame 250. Following this configuration, the motion of thin hinge44 g-6′, which may be the weakest portion of cantilever 44, issubstantially limited during a shock event. For example, with the cagingstructure, hinge 44 g-6′ may displace about 10 times less in the ydirection. In alternative embodiments, protrusion 520 may terminatebelow end 44 g-3′ of the forked junction 44 g-1′ or even further.

The length of protrusion 520 and the vertical gap between forkedjunction 44 g-1′ and caging structure 500 may be tuned in variousembodiments to maximize the amount of shock protection provided whileensuring that cantilever 44 has enough space to move during regularoperation. In specific embodiments, protrusion 520 may be between 150and 300 micrometers long, and the gap between end 44 g-4′ and cagingstructure 500 (below or above the forked junction) may be between 3 and20 micrometers.

FIG. 4D illustrates a shock caging structure 600 for caging a motioncontrol flexure 24 in accordance with an embodiment. A caging structure600 (e.g., a rigid silicon structure) surrounds an end of motion controlflexure 24. In this embodiment, caging structure 600 is a part of amoving frame 22 a of a comb drive actuator 20.

Caging structure 600 includes a protrusion 620 to the side of hinge 24-2that extends parallel to and past the hinge. In this example, protrusion620 terminates at an end of rod 24-1 of motion control flexure 24.Accordingly, in the event of a shock, the end of rod 24-1 contacts stiffprotrusion 620 and does not horizontally displace in the left xdirection past stiff protrusion 620 or in the right x direction pastframe 22 a. Following this configuration, the motion of thin hinge 24-2,which may be the weakest portion of motion control flexure 24, issubstantially limited during a shock event. For example, with the cagingstructure 600, hinge 24-2 may displace about 10 times less in the xdirection.

The length of protrusion 620 and the horizontal gap between the end ofrod 24-1 and caging structure 600 may be tuned in various embodiments tomaximize the amount of shock protection provided while ensuring thatflexure 24 has enough space to move during regular operation. Inspecific embodiments, protrusion 620 may be between 100 and 225micrometers long, and the gap between rod 24-1 and caging structure 600(to the left or right of the rod) may be between 4 and 20 micrometers.

FIG. 4E illustrates a shock caging structure 700 for caging a motioncontrol flexure 24 in accordance with an embodiment. A caging structure700 (e.g., a rigid silicon structure) surrounds an end of motion controlflexure 24. In this embodiment, caging structure 700 is a part of afixed frame 22 b of a comb drive actuator 20. Frame 22 b surrounds anend of rod 24-1 of motion control flexure 24. Accordingly, in the eventof a shock, the end of rod 24-1 does not horizontally displace past thewalls of the frame. Following this configuration, the motion of thinhinge 24-2, which may be the weakest portion of motion control flexure24, is substantially limited during a shock event.

FIG. 5A illustrates an example model at a moment during a mechanicalshock event of a MEMS actuator including shock caging structures for itscantilevers 44 and motion control flexures 24. The shock cagingstructures limit the motion experienced by cantilevers 44 and motioncontrol flexures 24. Less stress is placed on the hinges of cantilevers44 and flexures 24. FIG. 5B illustrates an example model at a momentduring a mechanical shock event of a MEMS actuator not including shockcaging structures for its cantilevers 44 and motion control flexures 24.Without the shock caging structures, cantilevers 44 and motion controlflexures 24 freely flail and oscillate between the moving frames. Thehinges of cantilevers 44 and motion control flexures 24 experiencegreater stress.

FIG. 6A is a top view illustrating an image sensor 800 mounted on a MEMSactuator 1000 including moving frame 1100. FIG. 6B illustrates a packagehousing 900 for covering the image sensor 800 on MEMS actuator 1000.FIGS. 6C-6E illustrate cross-sections of an assembled actuatoroptoelectronic package including the components of FIGS. 6A-6B. Asshown, package housing 900 includes shock stops 910 and 920 that reducethe gap between component 1150 of moving frame 1100 and the back ofpackage housing 900. Stops 910 and 920 may prevent the moving frame 1100from moving excessively out of plane during a mechanical shock event,which may deform any motion control beams (e.g., cantilevers) of theactuator. In embodiments, the shock stops may be made of a suitableplastic.

FIG. 7 is an exploded perspective view illustrating an assembled movingimage sensor package 55 that may use the mechanical shock reductionfeatures described herein in accordance with one embodiment. Inembodiments, moving image sensor package 55 may be a component of aminiature camera (e.g., a miniature camera for a mobile device). Movingimage sensor package 55 can include, but is not limited to the followingcomponents: a substrate 73; a plurality of capacitors and/or otherpassive electrical components 68; a MEMS actuator driver 69; a MEMSactuator 57; an image sensor 70; an image sensor cap 71; and an infrared(IR) cut filter 72. Substrate 73 can include a rigid circuit board 74with a recess 65 and in-plane movement limiting features 67, and aflexible circuit board acting as a back plate 66. The rigid circuitboard 74 may be constructed out of ceramic or composite materials suchas those used in the manufacture of plain circuit boards (PCB), or someother appropriate material(s). Moving image sensor package 55 mayinclude one or more drivers 69.

Since the thermal conduction of air is roughly inversely proportional tothe gap, and the image sensor 70 can dissipate a substantial amount ofpower between 100 mW and 1 W, the gaps between the image sensor 70, thestationary portions of the MEMS actuator 57, the moving portions of theMEMS actuator 57, and the back plate 66 are maintained at less thanapproximately 50 micrometers. In one embodiment, the back plate 66 canbe manufactured out of a material with good thermal conduction, such ascopper, to further improve the heat sinking of the image sensor 70. Inone embodiment, the back plate 66 has a thickness of approximately 50 to100 micrometers, and the rigid circuit board 74 has a thickness ofapproximately 150 to 200 micrometers.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not of limitation. Likewise, the various diagrams maydepict an example architectural or other configuration for theinvention, which is done to aid in understanding the features andfunctionality that can be included in the invention. The invention isnot restricted to the illustrated example architectures orconfigurations, but the desired features can be implemented using avariety of alternative architectures and configurations. Indeed, it willbe apparent to one of skill in the art how alternative functional,logical or physical partitioning and configurations can be implementedto implement the desired features of the present invention. Also, amultitude of different constituent module names other than thosedepicted herein can be applied to the various partitions. Additionally,with regard to flow diagrams, operational descriptions and methodclaims, the order in which the steps are presented herein shall notmandate that various embodiments be implemented to perform the recitedfunctionality in the same order unless the context dictates otherwise.

Although the invention is described above in terms of various exemplaryembodiments and implementations, it should be understood that thevarious features, aspects and functionality described in one or more ofthe individual embodiments are not limited in their applicability to theparticular embodiment with which they are described, but instead can beapplied, alone or in various combinations, to one or more of the otherembodiments of the invention, whether or not such embodiments aredescribed and whether or not such features are presented as being a partof a described embodiment. Thus, the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as meaning “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; the terms “a” or“an” should be read as meaning “at least one,” “one or more” or thelike; and adjectives such as “conventional,” “traditional,” “normal,”“standard,” “known” and terms of similar meaning should not be construedas limiting the item described to a given time period or to an itemavailable as of a given time, but instead should be read to encompassconventional, traditional, normal, or standard technologies that may beavailable or known now or at any time in the future. Likewise, wherethis document refers to technologies that would be apparent or known toone of ordinary skill in the art, such technologies encompass thoseapparent or known to the skilled artisan now or at any time in thefuture.

The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other like phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent. The use of theterm “module” does not imply that the components or functionalitydescribed or claimed as part of the module are all configured in acommon package. Indeed, any or all of the various components of amodule, whether control logic or other components, can be combined in asingle package or separately maintained and can further be distributedin multiple groupings or packages or across multiple locations.

Additionally, the various embodiments set forth herein are described interms of exemplary block diagrams, flow charts and other illustrations.As will become apparent to one of ordinary skill in the art afterreading this document, the illustrated embodiments and their variousalternatives can be implemented without confinement to the illustratedexamples. For example, block diagrams and their accompanying descriptionshould not be construed as mandating a particular architecture orconfiguration.

What is claimed is:
 1. A microelectromechanical systems (MEMS) actuator,comprising: an outer frame coupled to an inner frame by a beam; the beamwhich couples the outer frame and the inner frame, comprising: a centerportion comprising a first end and second end; a first hinge directlycoupled to the first end of the center portion; and a second hingedirectly coupled to the second end of the center portion, wherein thefirst hinge and the second hinge are thinner than the center portion;and a silicon caging structure at least partially surrounding, inparallel, at least one of the first hinge and the second hinge directly,wherein the silicon caging structure limits a maximum displacement ofthe beam in a direction perpendicular to a longitudinal axis of thebeam.
 2. The MEMS actuator of claim 1, wherein the beam is a conductivecantilever, and wherein the center portion is curved and comprises apoint of inflection.
 3. The MEMS actuator of claim 1, wherein the beamis a motion control flexure, and wherein the center portion is taperedalong its length such that it is widest at its center and narrowest atits ends.
 4. The MEMS actuator of claim 1, wherein each of the firsthinge and second hinge is tapered along its length such that isnarrowest at its center and widest at its ends.
 5. The MEMS actuator ofclaim 1, wherein the beam is between 1 and 7 millimeters long andbetween 10 and 70 micrometers wide, and wherein the beam is rigid in adirection along its length and flexible in a direction perpendicular toits length.
 6. A microelectromechanical systems (MEMS) device,comprising: a beam, comprising: a center portion comprising a first endand second end; a first hinge directly coupled to the first end of thecenter portion; and a second hinge parallel to the first hinge anddirectly coupled to the second end of the center portion, wherein thefirst hinge and the second hinge are thinner than the center portion;and a silicon caging structure at least partially surrounding, inparallel, at least one of the first hinge and the second hinge directly,wherein the silicon caging structure limits a maximum displacement ofbeam in a direction perpendicular to a longitudinal axis of the beam. 7.The MEMS device of claim 6, wherein the beam is rigid in a directionalong its length and flexible in a direction perpendicular to itslength.
 8. The MEMS device of claim 6, further comprising: a movingframe, wherein the silicon caging structure is part of the moving frame,and wherein at least one of the first hinge and the second hinge iscoupled to the moving frame.
 9. The MEMS device of claim 7, wherein thesilicon caging structure comprises: a protrusion extending parallel toand along the length of the first hinge or the second hinge, wherein theprotrusion limits the maximum displacement of the beam in a directionperpendicular to its length.
 10. The MEMS device claim 6, wherein eachof the first hinge and second hinge is tapered along its length suchthat is narrowest at its center and widest at its ends.
 11. The MEMSdevice of claim 10, wherein the center portion is tapered along itslength such that it is widest at its center and narrowest at its ends;12. The MEMS device of claim 6, wherein the MEMS device is an actuator,wherein the beam is a motion control flexure of the actuator, andwherein at least one of the first hinge and the second hinge is coupledto a frame of the actuator.
 13. The MEMS device of claim 12, wherein thefirst hinge is coupled to a fixed frame of the actuator, and wherein thesecond hinge is coupled to a moving frame of the actuator.
 14. The MEMSdevice of claim 6, wherein the center portion is between 1 and 4 mm longand between 10 and 70 μm wide, and wherein each of the first and secondhinges is between 0.05 and 0.3 mm long and between 1 and 10 μm wide. 15.The MEMS device of claim 6, wherein the beam is a conductive cantilever,wherein the center portion is curved and comprises a point ofinflection.
 16. The MEMS device of claim 15, wherein the length of thecantilever is between 4.5 and 7 millimeters, and wherein the centerportion is between 0.012 and 0.030 millimeters wide.
 17. The MEMS deviceof claim 15, wherein each of the first and second hinges is coupled tothe center portion by a respective forked junction in a directionperpendicular to the length of the cantilever, wherein the forkedjunction comprises a plurality of parallel beams.
 18. The MEMS device ofclaim 17, wherein the silicon caging structure comprises: a protrusionextending parallel to and along the length of the first hinge or thesecond hinge, wherein the protrusion limits the maximum displacement ofthe cantilever in a direction perpendicular to its length, wherein thecantilever reaches its maximum perpendicular displacement when theprotrusion contacts one of the forked junctions.